In radiotherapy, for example as practiced in x-ray oncology, a precise amount of radiation, or dose, must be delivered to an accurately and precisely defined portion of a patient's body. However, since high levels of high energy radiation are used during radiation therapy treatment, exposure to the radiation by both medical personnel and the patient should be limited.
Stationary and mobile x-ray examination devices are known which have a C-arm with opposing ends having an x-ray radiation source and a radiation receiver (e.g., an image intensifier), respectively. The C-arm can be readily located so that transirradiation of a patient oriented on a table is possible from a variety of different directions. The table is typically adjustable in three dimensions (i.e., in x-, y-, and z-spatial dimensions).
Radiation treatment plans are designed to maximize radiation delivered to a target while minimizing radiation delivered to healthy tissue. However, even if such a plan is designed, the goals of maximizing target radiation and minimizing healthy tissue radiation may not be achieved if the radiation is not delivered exactly as required by the treatment plan. More specifically, radiation delivery errors as well as poor treatment planning can result in low irradiation of tumors and high irradiation of sensitive healthy tissue. Thus, x-ray examination devices for the transirradiation of a patient must be arranged relative to the patient such that the x-ray source and the radiation receiver lie in the imaging field of the radiation receiver.
However, prior attempts to provide a visible indication of the location of an invisible x-ray beam have been unsuccessful. Such systems are either inaccurate or produce artifacts on imaging screens of the medical devices. The artifacts produced are indicative of hardware used to produce the visible indicators.